Author(s): Takeyoshi Chibana; Hidehito Iwamoto; Tetsuro Tsujimoto
Linked Author(s):
Keywords: Riffle; Wave pattern; Hierarchical structure of physical environment
Abstract: Riffles have diverse environment and are utilized by several kinds of aquatic creatures. The diverse environment in a riffle is expressed as the diverse texture of its water surface, but there are some patterns of the texture. Therefore it is conceivable that the physical conditions in a riffle can be classified into several groups based on the texture of water surface. In this paper, we analyzed the relationship between physical conditions and landscape of a riffle that was composed of several wave patterns. At first, wave patterns which are the elements of landscape of a riffle were investigated. They were categorized into nine patterns in consideration of spatial scale of each wave. Every wave type is generated by different fluid and riverbed property, hence the distribution of hydraulic and riverbed configurations in a riffle that determine wave patterns was also investigated. Riverbed configurations were represented by mean diameter and roughness of the riverbed. After some field observations and hydraulic experiments, it was clarified that the physical elements which determined wave patterns were Froude number (Fr), the ratio of mean depth to mean gravel diameter (h/d), water surface slope (Iw), and gravel protrusion ratio to mean riverbed surface (dp/h). Then the condition of each wave pattern was clarified by using these factors. Finally, we showed that the physical environment in riffles can be classified visually based on the wave patterns.
Year: 2005